The aims of this project remain to provide an understanding in molecular terms of the roles of lymphocytes and macrophages in cell-mediated immunity. The approach will place major emphasis on cloned cell lines expressing specific macrophage or lymphocyte functions, and the use of genetic techniques to select of variants in specific functions. A major effort will be made to pursue these aims using human cell lines studied within the context of a unique human disease model, leprosy. To better understand the immunoregulatory changes occurring in lepromatous leprosy patients who are specifically unresponsive to lepromin, we propose to establish T-helper and T-suppressor cell lines, to define the requirements for in vitro sensitization of normal T cells to mycobacterial antigens, and those for in vitro induction of T-suppressor cells, and analyzing the specificity and mode of action of the T-suppressor cells on vitro sensitization, particularly production of suppressor factors. To better understand bactericidal effector mechanisms, we propose to develop human monocyte/macrophage cell lines, study macrophage cytocidal mechanisms through the use of variants in oxygen metabolism, develop a cell-free system for in vitro production of O2-, characterize the critical membrane enzymes, and define the mechanisms of priming and triggering for an oxidative burst. Attempts will be made to reconstitute these lines with enzymes and drugs to enhance intracellular cytocidal activity. Finally, a variety of variants in macrophage cell lines defective in interferon responsiveness, cytoskeletal functions and lysosomal enzymes will be studied to define critical cellular requirements for antigen presentation and activation for intracellular killing.